I'm using RubyMine #472. Go into Settings -> Inspections -> Ruby ->
Unresolved Ruby reference (though the exact item doesn't appear to
matter). In the Options area click the settings box. On any of the
four built-in Severities (ERROR, WARNING, INFO, SERVER PROBLEM) there is
a button to "Edit Settings|Colors & Fonts". Clicking on that button
takes me to a blank screen in Settings.
I have spent quite a while trying to edit those colors because, on a
black background with white default text, they are completely
unreadable. As far as I can tell there isn't any place in the Settings
where those colors can be edited. None of the options under Settings ->
Editor -> Colors & Fonts seems to affect those Severities.